Home-based parenting programs aimed at improving a child's health and well-being have demonstrated success across a range of outcomes. However, the degree to which other children in the home also benefit from these programs via changes in parental attitudes and behaviors has not been rigorously investigated. This topic has far-reaching implications for promoting positive youth development and preventing emotional and behavioral problems, particularly in low-resource settings in which family sizes are large, children often face significant adversity, and access to mental health services is extremely limited. A randomized controlled trial with a promising caregiver training intervention for vulnerable populations, the Mediational Intervention for Sensitizing Caregivers (MISC), has already been funded to investigate the intervention impact on neurodevelopmental, psychological and social outcomes (MPI: Bass, Boivin: 1R01HD070723-01) among HIV-infected and HIV-affected young children (ages 2-5). Study Methods With on average 2.7 children under age 12 years living in our study homes, we expect to recruit approximately 170 children in the MISC homes and 170 children in the control homes to investigate dispersion effects of the MISC program to other children in the home, using the HIV-affected study cohort. The specific child outcomes that will be investigated include: development gains on the Mullen, the Behavior Rating Inventory of Executive Functioning (BRIEF), and the caregiver administered version of the Achenbach CBCL, physical health measures of growth and development, and school participation. Family level outcomes that will be investigated include as part of this supplement include family functioning assessed using the McMaster Family Assessment Device (FAD), family size, and familial relationships through the use of a household diagram. The specific aims of this supplement grant are: Aim 1: To evaluate whether caregiver training produces greater improvements in functioning among non-R01 study children in the MISC homes compared with non-R01 study children in the control homes. Aim 2: To assess potential mediators of the association between caregiver training and non-R01 study child outcomes. Aim 3: To assess potential moderators of the association between caregiver training and outcomes in the non-R01 study children, including child age, child sex, caregiver health, and family size. Innovation and impact This supplement innovates beyond the parent R01 by rigorously testing the MISC intervention's potential to benefit multiple children in the home. Given relatively large family sizes in Uganda and severe financial and human resource limitations, a caregiver intervention that improves the well-being of multiple children is a promising program for nation-wide scale up. Information gained through the exploration of mediators and moderators will allow further intervention adaptation to maximize intervention effectiveness to more than just a single study child. Broadly, this study is responsive to recent calls for innovative strategies to address what has been termed a global mental health crisis in which mental health needs far outpace available services in low-resource settings. As such, findings have exciting potential for application with other high-risk populations internationally.